C1300 lnter trouble

Hi all
I have a c1300 inter with a 6 cylinder 281 engine which normally runs good .
I started the truck yesturday and it idle rough.The truck had just over 1/4 tank of fuel so l dove the truck to the servo and put 20 dollars in the tank.driving the truck it had no power and was backfiring.
Could it be the fuel as l have know started the truck for a month?

I drove the truck today and it was a little better nowever not running as it should

Any help would be great
Thanks
Steve

Try spark plugs and check that the points gap is good.

I've been Having similiar trouble, turned out to be a crook fuel pump and air leaks in the fuel lines, fitted an electric pump and repaired fuel lines going really good now, check the fuel pickup line in the tank and clean the tank out

Steve could be sucking air in fuel line before the pump as we had the same with the R180 running well and when it got down to half a tank it started doing as you have described, we where blaming the electrics, couldn't fix it. Anyway to cut along story short when I lifted the cab off the connection on top of the fuel tank was very loose, also sucking air on the vacuum side will do much the same.
Colin